There are fears he could be out until after the next international break which would mean no return until mid-November.

That would see him miss the Premier League games with Watford, Everton, Swansea and Man City. He would also be unavailable for the League Cup match with Norwich and Europa League ties against Crvena Zvezda.

The importance of Mustafi to the side has been highlighted by their recent run of form. The German returned to the centre of a back-three following the 4-0 defeat to Liverpool and Arsenal haven’t conceded in the Premier League since. They’ve kept clean sheets against Bournemouth, Chelsea, West Brom and Brighton with Mustafi anchoring the side.

So what could Arsene Wenger do in his absence to keep a tight defence?

Holding comes in

The simplest solution is a straight swap with Rob Holding coming into the side to replace Mustafi. The youngster has been the most used of the alternative options, with Calum Chambers currently injured and Per Mertesacker yet to play in the Premier League this season. Holding might not be trusted to play the central role though, so Laurent Koscielny could move across with Holding playing on the right of a back three.

Rob Holding with Petr Cech (Getty)

While Holding is the most logical choice, Wenger will be concerned that it was Monreal-Koscielny-Holding at the back in that embarrassing defeat at Anfield. However, on that afternoon Bellerin was playing on the left with Alex Oxlade-Chamberlain on the right.

Switch formation and play it safe

Wenger seems to be a convert to playing three at the back this season, having done so in every game so far. But in the two matches in which Mustafi has absent Arsenal have conceded a total of seven goals. It suggests they might not be capable of functioning in the system without the German.

Mustafi has been impressive in recent weeks (Getty)

So perhaps time to revert to a back-four. Sead Kolasinac on the left and Hector Bellerin on the right pick themselves. Koscielny will then come in but who would be best to partner him is debatable. Holding or Mertesacker are the obvious options with the latter probably the safest choice.

Switch formation and mix it up

Instead of playing a traditional centre-back Wenger could drop Mohamed Elneny into the role. He did so in pre-season and clearly trusts the Egyptian.

‘When he plays there, of course he does extremely well,’ Wenger said over the summer. ‘Of course [he needs to learn the defensive side], but I always felt that a good central midfielder can be a good centre back.’

Mohamed Elneny is an option (Getty)

If Wenger wanted to add a little more solidity to his side he could play Monreal at left-back and deploy Kolasinac on the left of midfield. The Bosnian would bring some steel to the side and has already shown his qualities going forward.